The applicant proposed a rail guided vehicle system for which it is not necessary to change the positions of adjustable rollers in height when a rail guided vehicle travels straight through a branching part (for example, Patent Literature 1: JP2005-186843A). The arrangement of a guide part on a travelling rail according to Patent Literature 1 is shown in FIG. 12. Reference numeral 7 denotes a side wall of the travelling rail. The guide part protrudes downward from the upper part of the travelling rail, reference numeral 12 denotes a protruding part where the guide part protrudes deeply downward, and reference numeral 13 denotes a normal part where the guide part protrudes to a normal position. The rail guided vehicle (not shown) is provided with right and left adjustable rollers in height, and the right and left adjustable rollers in height are raised or lowered in a manner opposite to each other. Note that, in this specification, right and left directions, or lateral direction is horizontally perpendicular to the travelling direction. In an advanced state in which the adjustable rollers in height are raised upward, the adjustable rollers in height are guided by both the protruding part 12 and the normal part 13. Also, in a retracted state in which the adjustable rollers in height are lowered, the adjustable rollers in height are not guided by either the protruding part 12 or the normal part 13. In an intermediate state in which the adjustable rollers in height are halfway between the advanced state and the retracted state, the adjustable rollers in height are guided only by the protruding part 12.
In FIG. 12, the rail guided vehicle travels from left to right in the figure, and when the rail guided vehicle travels straight through a branching/merging part, control of the adjustable rollers in height is not necessary. In a case of branching from the lower travelling rail in FIG. 12, it is necessary that the height adjustable roller on the left side with respect to the travelling direction is raised before the rail guided vehicle reaches the normal part 13a, and the height adjustable roller on the right side with respect to the travelling direction is raised before the normal part 13a terminates at the merging part. However, changing the positions of the adjustable rollers in height is not accomplished in time in a short branching/merging part, and thus the rail guided vehicle needs to stop or slow down in the branching/merging part. In JP2005-186843A, when the rail guided vehicle travels only through the branching part or the merging part, it is sufficient that the positions of the adjustable rollers in height are changed before the branching part or the merging part is reached. However, when the rail guided vehicle travels through a branching/merging part into which the branching part and the merging part are integrated, the rail guided vehicle needs to slow down or stop. Patent Literature 1 does not take in consideration travelling through the branching/merging part in which the branching part and the merging part are arranged in a continuous manner.